1. Field of the Invention
This invention generally relates to a claw pole generator. More specifically, the present invention relates to a claw pole generator, especially for a bicycle generator hub that is contrived to suppress the occurrence of eddy currents.
2. Background Information
Bicycle generator hubs are known that uses a claw pole type generator. Generally, a conventional claw pole generator has a yoke having first and second laminated yokes. Each laminated yokes has a plurality of plate-like pieces laminated together. In a conventional claw pole generator with laminated yokes, each of the plate-like pieces has a pair of circular disc-like portions and outer circumferential yoke portions. The outer circumferential yoke portions are formed in a radial fashion on and folded over from a peripheral edge of the circular disc-like portion so as to intersect generally perpendicularly with respect to the circular disc-like portion (e.g., Japanese Laid-Open Patent Publication No. 2004-229403). The lengths of the outer circumferential yoke portions of the plate-like pieces become longer as one moves inward and the positions of the tip ends thereof are aligned with respect to a radial direction.
In the conventional generator, the circular disc-like portions of the laminated plate-like pieces of the first and second laminated yokes are attached to a hub shaft on both ends of a coil so as to be separated from each other along an axial direction. The first and second laminated yokes are arranged such that the outer circumferential yoke portions of the laminated plate-like pieces of the first laminated yoke are alternately interdisposed with respect to the outer circumferential yoke portions of the laminated plate-like pieces of the second laminated yoke with the tip ends of the outer circumferential yoke portions of the first laminated yoke facing in the opposite direction as the tip ends of the outer circumferential yoke portions of the second laminated yoke.
In the conventional generator, the outer circumferential yoke portions of the plate-like pieces of the laminated yokes are arranged to be separated by a small gap from the permanent magnet that is fixed to a hub shell in order to increase a generating efficiency. By configuring the yoke to have first and second laminated yokes arranged with the outer circumferential yoke portions interdisposed in an alternating fashion, losses caused by eddy currents can be decreased and the output can be improved. Examples of two conventional generators are discloses in Japanese Laid-Open Utility Model Publication No. H03-117357 and Japanese Examined Utility Model Application Publication No. 32-8026.